Usually, a dry etching exhaust gas containing a halogen series gas (hereinafter referred to sometimes as the present halogen series gas) of a group consisting of F2, Cl2, Br2, I2, and compounds which generate a hydrogen halide or hypohalogeneous acid upon hydrolysis, a CVD (Chemical Vapor Deposition) chamber exhaust gas containing a SiH4 (silane) gas as the main component, and an ion implantation or doping exhaust gas containing AsH3 (arsine) or PH3 (phosphine) as the main component, contain the above-mentioned main component gases together with a carrier gas such as N2 (nitrogen) gas, and a halogen series gas or particles formed by decomposition or reaction of such main component gases in a production apparatus.
Heretofore, as a method for treating the above-mentioned present halogen series gas, a dry type treating method using an adsorbent made of activated carbon as a packing material has been frequently used in order to make the apparatus smaller or to simplify the operation and maintenance of the apparatus. However, with such a treating method, there have been various problems such as, along with a danger of fire by heat of adsorption of a gas to be treated, degradation of working environment at the time of exchanging the packing material due to an odor of the present halogen series gas desorbed from a used adsorbent, and treatment of a solid waste, and it has been desired to solve such problems. Also, it has been desired to further increase the adsorption capacity of the packing material in order to reduce the frequency of exchanging operation of the packing material. These problems were particularly noticeable at the time of removing a Cl2 gas or a gas mixture of Cl2 and BCl3 (boron trichloride), which has been frequently used.
In order to solve the above problems in the dry type treating method using an adsorbent made of activated carbon, a method for removing a halogen series gas by using a granule obtained by granulating a powder of a hydrogencarbonate, is suggested (e.g. Patent Document 1).
However, with the removing method described in Patent Document 1 wherein the present halogen series gas is removed only by a solid base, if the present halogen series gas is F2, Cl2, Br2 or I2, there is a concern that by formation of a hypohalogenite, a neutralization reaction will be hindered, and the treating capacity will decrease.
Further, a method for removing the present halogen series gas by using a removing agent made of a mixture of a solid base and activated carbon, is suggested (e.g. Patent Document 2). According to the removing method described in Patent Document 2, by using the removing agent made of the above mixture, it is possible not only to solve the above described problems such as a danger of fire by heat of adsorption of a gas to be treated, degradation of working environment due to an odor from the used adsorbent, and treatment of a solid waste, but also to increase the adsorption capacity of the packing material and to reduce the frequency of exchanging operation of the packing material.
However, with the removing method described in Patent Document 2, the sufficient removing ability can be shown in a case of removing the present halogen series gas having a high concentration, but the sufficient removing ability cannot be shown in a case of removing the present halogen series gas having a low concentration of e.g. approximately at most 5 vol %.
Further, as the removing agent for removing the present halogen series gas, one containing calcium hydroxide and thiosulfate is suggested (e.g. Patent Document 3).
However, like in the case of such a removing agent described in Patent Document 3, if the removing agent is constituted by the above calcium hydroxide as a main component, the heat generation value during the neutralization reaction will be large, and the reaction efficiency between the removing agent and a hydrogen halide will decrease, whereby there is a concern that a large amount of calcium hydroxide will remain as unreacted. Further, the solubility of the calcium hydroxide in water is extremely low, whereby when the used removing agent is treated, it is difficult to reduce the volume by dissolving the agent in water.
Patent Document 1: U.S. Pat. No. 6,685,901
Patent Document 2: WO03/033115
Patent Document 3: JP-A-2001-17831